System for distributing a signal between loudspeaker drivers
A system for distributing a source voltage from a signal source to a number of drivers or loudspeakers is disclosed. The system includes at least one autotransformer for connection to the signal source, and a number of drivers electrically connected to the autotransformer. The autotransformers distribute the source voltage across each of the drivers. The autotransformers produce an output voltage across each of the drivers, such that the sum of the output voltages is substantially equal to the source voltage multiplied by the number of drivers.
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This invention relates to loudspeakers, and more particularly to a system for distributing a signal or voltage to loudspeaker drivers.
BACKGROUND OF THE INVENTIONIt is well known to provide a loudspeaker unit which includes two or more individual speakers (also known as drivers) to cover different sections of the frequency spectrum. Loudspeakers with multiple drivers are desirable because a single driver large enough to provide adequate response at low frequencies is not capable of providing an adequate response at higher frequencies. Such systems are commonly known as two or three way systems, depending upon whether a separate driver is provided to cover two or three different frequency portions, respectively.
Moreover, in some known designs where higher efficiency is a concern, multiple drivers may be provided in each crossover section or for each frequency band. It is not uncommon to have up to three drivers or speakers in a low pass section and even two drivers in a midrange section.
A disadvantage to a loudspeaker having multiple drivers is that the drivers occupy more space, and can narrow the spatial characteristics of the system. For example, the sound from multiple speakers or drivers can appear to be more directional than from a single driver. This effect is more pronounced at higher frequencies.
One known technique for reducing this disadvantage of multiple drivers is to differentiate the signals fed to the individual drivers in one section. This is achieved by setting different low pass cutoff frequencies for each driver and this is common practice where multiple drivers are provided. The effect of this technique is to reduce the number of drivers participating in sound reproduction at higher frequencies, thereby improving sound dispersion.
However, this technique has a number of disadvantages. One of the disadvantages is lower efficiency, since at higher frequencies fewer drivers are radiating the sound. Another disadvantage is that is difficult to achieve a flat frequency response, because of a complex phase relationship between drivers connected to different low pass filters. Even if systems employing low pass filters are designed, using simple mathematical addition, to produce a flat frequency response, in practice, such systems often introduce unwanted and varying phase shifts. At higher frequencies, these phase shifts can be even more pronounced, and, result in a reduced signal level.
Accordingly, there is a need for a loudspeaker system to simply and efficiently distribute an input signal between a number of drivers. There is a further need for a system which enables different low pass cut off frequencies to be set for the drivers, while enabling a more flat, total frequency response to be provided.
SUMMARY OF THE INVENTIONThe loudspeaker system according to the present invention utilizes a tapped coil or autotransformer to divide a signal between different drivers. While such autotransformers are known, they have never been used for such a purpose.
According to the present invention, a system for distributing a source voltage from a signal source is provided. The system comprises at least one autotransformer for connection to the signal source, and a plurality of drivers electrically connected to the autotransformer. The autotransformer is adapted to distribute the source voltage across each of the plurality of drivers. Preferably, the autotransformer is adapted to produce an output voltage across each of the drivers, wherein the sum of the output voltages is substantially equal to the source voltage multiplied by the number of drivers.
For a better understanding of the present invention and to show more clearly how it may be carried into effect, reference will now be made by way of example to the accompanying drawings, which show a preferred embodiment of the present invention and in which:
Continuing to refer to
u2=2·u1 (1)
This type of connection is known as a “center tap” connection.
The inventor has discovered that the sum of the output voltages V1 and V2 remain constant, disregarding the load impedances. If the loads are identical, then each of the voltages V1, V2 are identical and equal to the source voltage E. More specifically, if the source voltage is E, then the relationship between input and output voltages is described by the following equation:
V1+V2=2E (2)
This relationship between the input and output voltages remains constant, even if the loads are varied. Thus, if the impedance is varied so that one voltage, e.g., V1, decreases, the other voltage V2 increases to maintain the relationship indicated by the equation (2) above.
Referring to
The first capacitor 24 provides a cutoff frequency for the second driver 20. In effect, as the frequency increases, the combined impedance of the driver 20 and the first capacitor 24 drops, and a greater portion of the current passes through the first capacitor 24. Consequently, the output voltage across the driver 20 is reduced. In accordance with equation 2 above, the output voltage across driver 18 increases to compensate for the voltage reduction across driver 20.
As the sound level generated by each driver 18, 20 corresponds to the voltage across it, the total sound level remains the same (because the sum of the voltages is constant).
This relationship is illustrated in
Referring to
The low pass filter 28 may be any known low pass filter, such as, an inductor 30 and a second capacitor 32 having values selected to give a desired low cut off frequency. For example, for a desired cut-off frequency of 2 kHz, the inductor 30 would have a value of 0.5 mH and second capacitor 32 would have a value of 12.6 uF. This embodiment is particularly suited for driving a pair of drivers 18, 20 which are low frequency speakers or woofers. Thus, at a desired cutoff frequency the low pass filter 28 cuts off or reduces the output voltage across the drivers 18, 20. Otherwise, the operation of this embodiment is similar to that described for
It is to be noted that while the low pass filter 28 is located before the autotransformer 10 in
While the first capacitor 24 shown in
Referring to
Continuing to refer to
V1+V2+V3=3E (3)
As before, the second driver 20 is provided with a first capacitor 24, with a value of for example 50 microfarads, to give a low cutoff frequency. A second capacitor 50 is connected to the third driver 40. The second capacitor may be configured for any suitable cutoff frequency, such as, for example 100 mircrofarads to give an even lower cutoff frequency.
The frequency response of this embodiment is illustrated in
Yet another embodiment of the present invention is shown in
V1+V2+V3+V4=4E (4)
It will be understood by those skilled in the art that the relationship described by equations (2), (3), and (4) above and the system according to the present invention may be extended to any number of drivers.
V1+V2+V3+ . . . Vn=nE (4)
where n is the total number of drivers connected to signal source 22.
Continuing to refer to
Various elements and networks may be added to the system shown in
The loudspeaker system according to the present invention utilizes one or more autotransformers, such as a tap coil, to distribute the input signal received by a number drivers. The use of one or more autotransformers to distribute the input signal or voltage provides the advantage of a more flat frequency response from the drivers. Specifically, the sum of the voltages across each driver is constant, regardless whether one or all of the drivers are producing sound. This sum is equal to the source voltage multiplied by the number of drivers. The present invention is particularly useful for loudspeaker systems which are designed such that only a portion of the drivers produce an acoustic signal in a particular frequency range, such as at high frequencies. In such systems, the voltages across the drivers in use increase to preserve the acoustic level of the system.
While the above description constitutes the preferred embodiments, it will be appreciated that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof.
Claims
1. A system for distributing a source voltage from a signal source, the system comprising:
- a) at least one autotransformer comprising: i) a tap connection adapted for electrical connection to said signal source; ii) a first end connection; iii) a second end connection, wherein said tap connection is located between said first end connection and said second end connection; and
- b) a plurality of drivers electrically connected to said at least one autotransformer;
- wherein said first end connection is electrically connected to a first one of said plurality of drivers and said second end connection is electrically connected to a second one of said plurality of drivers or a second of said at least one autotransformer, wherein said at least one autotransformer is adapted to distribute said source voltage across each of said plurality of drivers;
- wherein the turn ratio of said at least one autotransformer is (n−x):1, where n is the number of said plurality of drivers and x is the position of said at least one autotransformer from said signal source.
2. The system of claim 1, wherein said at least one autotransformer is adapted to produce an output voltage across each of said plurality of drivers, each of said plurality of drivers being adapted to convert said corresponding output voltage to an acoustic signal, wherein the sum of said output voltages is substantially equal to said source voltage multiplied by the number of said plurality of drivers.
3. The system of claim 2, wherein said at least one autotransformer comprises a plurality of autotransformers, wherein the number of said plurality of autotransformers is one less than the number of said plurality of drivers.
4. The system of claim 3, wherein said first end connection of each of said plurality of autotransformers is electrically connected to a corresponding one of said plurality of drivers, said second end connection of a distally positioned one of said plurality of autotransformers being electrically connected to one of said plurality of drivers, said second end connection of a remaining portion of said plurality of autotransformers being connected to the tap connection of an adjacently positioned one of said plurality of autotransformers.
5. The system of claim 4, wherein the turn ratio of each of said plurality of autotransformers is (n−x):1, where n is the number of said plurality of drivers and x is the position of a selected one of said plurality of autotransformers form said signal source.
6. The system of claim 5, wherein said plurality of autotransformers comprises a first and second autotransformer and said plurality of drivers comprises a first, second, and third driver, wherein said first end connection of said first autotransformer is electrically connected to said first driver and said second end connection of said first autotransformer is electrically connected to said second driver, wherein said first end connection of said second autotransformer is electrically connected to said third driver and said second end connection of said second autotransformer is electrically connected to said tap connection of said first autotransformer, wherein said tap connection of said second autotransformer is electrically connected to said signal source, said first auto-transformer having a turn ratio of 1:1, said second autotransformer having a turn ratio of 2:1.
7. The system of claim 6, further comprising a first and second low pass filter, said first low pass filter being electrically connected between said first autotransformer and said second driver, said second low pass filter being electrically connected between said second autotransformer and said third driver, each of said first and second low pass filters being adapted to reduce said corresponding output voltage at different cutoff frequencies.
8. The system of claim 2, further comprising at least one first filter means for reducing said output voltage at a predetermined frequency, said at least one filter means being electrically connected to at least one of said plurality of drivers.
9. The system of claim 8, wherein said filter means is connected in parallel to said at least one of said plurality of drivers.
10. The system of claim 9, wherein said at least one filter means comprises a low pass filter.
11. The system of claim 10, wherein said low pass filter comprises a capacitor electrically connected said at least one driver.
12. The system of claim 11, wherein said low pass filter further comprises an inductor in combination with said capacitor.
13. The system of claim 11, wherein said low pass filter comprises a resistor in combination with said capacitor.
14. The system of claim 9, further comprising a plurality of low pass filters, each of said plurality of low pass filters being electrically connected to a corresponding one of at least a portion of said plurality of drivers.
15. The system of claim 14, wherein at least a portion of said plurality of low pass filters have different cutoff frequencies.
16. A system for distributing a source voltage from a signal source, the system comprising:
- a) at least one autotransformer comprising: i) a first end connection adapted to produce a first output voltage; ii) a second end connection adapted to produce a second output voltage; and iii) a tap connection adapted for electrical connection to said signal source, wherein said tap connection is located between said first end connection and said second end connection;
- b) a first driver electrically connected to said first end connection, wherein said first output voltage is received by said first driver solely from said first end connection; and
- c) a second driver electrically connected to said second end connection, wherein said second output voltage is received by said second driver solely from said second end connection;
- wherein the turn ratio of said at least one autotransformer is (n−x):1, where n is the number of said plurality of drivers and x is the position of said at least one autotransformer from said signal source.
17. The system of claim 16, further comprising a plurality of autotransformers and a plurality of drivers, wherein said plurality of autotransformers are adapted to produce an output voltage across each of said plurality of drivers, wherein the sum of said output voltages is equal to said source voltage multiplied by the number of said plurality of drivers.
18. The system of claim 17, wherein said plurality of autotransformers comprises said first autotransformer and a remaining portion of said plurality of autotransformers, wherein said first end connection of each of said remaining portion of said plurality of autotransformers is electrically connected to a corresponding one of said plurality of drivers, wherein said second end connection of said remaining portion of said plurality of autotransformers is electrically connected to said tap connection of an adjacently positioned one of said plurality of autotransformers.
19. The system of claim 18, wherein the turn ratio of each of said plurality of autotransformers is (n−x):1, where n is the number of said plurality of drivers and x is the position of a selected one of said plurality of autotransformers form said signal source.
20. The system of claim 19, wherein said plurality of autotransformers comprises said first autotransformer and a second autotransformer, wherein said plurality of drivers comprises said first driver, said second driver, and a third driver, wherein said first end connection of said second autotransformer is electrically connected to said third driver and said second end connection of said second autotransformer is electrically connected to said tap connection of said first autotransformer, wherein said tap connection of said second autotransformer is electrically connected to said signal source, wherein said first autotransformer has a turn ratio of 1:1 and said second autotransformer has a turn ratio of 2:1.
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Type: Grant
Filed: Aug 30, 2002
Date of Patent: Jan 31, 2006
Patent Publication Number: 20030063761
Assignee: Audio Products International Corp. (Scarborough)
Inventor: Stefan R. Hlibowicki (Toronto)
Primary Examiner: Vivian Chin
Assistant Examiner: Devona E. Faulk
Attorney: Bereskin & Parr
Application Number: 10/231,333
International Classification: H04B 3/00 (20060101); H03G 5/00 (20060101); H03F 21/00 (20060101);